Failure prediction for Titanium alloys using a superplastic forming limit diagram approach

Superplastic forming limit diagrams (SPFLDs) are presented for both Ti-6A1-4V and Ti-6A1-2Sn-4Zr-2Mo alloys. FE-predieted ε₁- ε₃-ε̇_eq paths for key points on the forming blank are then plotted on the SPFLD to predict failure, A key factor for reliable SPF forming limit prediction is the incorporation of a mechanisms-based constitutive model, which includes mierostruetural effects, such as static and dynamic grain growth and associated hardening, and with material constants independent of the forming strain-rate. The sinh model of Dunne and co-workers is thus employed. Results from forming trials for both materials are used to assess the failure predictions.